kernel/drivers/cpuidle/cpuidle-pseries.c

   1 /*
   2  *  cpuidle-pseries - idle state cpuidle driver.
   3  *  Adapted from drivers/idle/intel_idle.c and
   4  *  drivers/acpi/processor_idle.c
   5  *
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10 #include <linux/init.h>
  11 #include <linux/moduleparam.h>
  12 #include <linux/cpuidle.h>
  13 #include <linux/cpu.h>
  14 #include <linux/notifier.h>
  15
  16 #include <asm/paca.h>
  17 #include <asm/reg.h>
  18 #include <asm/machdep.h>
  19 #include <asm/firmware.h>
  20 #include <asm/runlatch.h>
  21 #include <asm/plpar_wrappers.h>
  22
  23 struct cpuidle_driver pseries_idle_driver = {
  24         .name             = "pseries_idle",
  25         .owner            = THIS_MODULE,
  26 };
  27
  28 static int max_idle_state;
  29 static struct cpuidle_state *cpuidle_state_table;
  30 static u64 snooze_timeout;
  31 static bool snooze_timeout_en;
  32
  33 static inline void idle_loop_prolog(unsigned long *in_purr)
  34 {
  35         ppc64_runlatch_off();
  36         *in_purr = mfspr(SPRN_PURR);
  37         /*
  38          * Indicate to the HV that we are idle. Now would be
  39          * a good time to find other work to dispatch.
  40          */
  41         get_lppaca()->idle = 1;
  42 }
  43
  44 static inline void idle_loop_epilog(unsigned long in_purr)
  45 {
  46         u64 wait_cycles;
  47
  48         wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
  49         wait_cycles += mfspr(SPRN_PURR) - in_purr;
  50         get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
  51         get_lppaca()->idle = 0;
  52
  53         if (irqs_disabled())
  54                 local_irq_enable();
  55         ppc64_runlatch_on();
  56 }
  57
  58 static int snooze_loop(struct cpuidle_device *dev,
  59                         struct cpuidle_driver *drv,
  60                         int index)
  61 {
  62         unsigned long in_purr;
  63         u64 snooze_exit_time;
  64
  65         idle_loop_prolog(&in_purr);
  66         local_irq_enable();
  67         set_thread_flag(TIF_POLLING_NRFLAG);
  68         snooze_exit_time = get_tb() + snooze_timeout;
  69
  70         while (!need_resched()) {
  71                 HMT_low();
  72                 HMT_very_low();
  73                 if (snooze_timeout_en && get_tb() > snooze_exit_time)
  74                         break;
  75         }
  76
  77         HMT_medium();
  78         clear_thread_flag(TIF_POLLING_NRFLAG);
  79         smp_mb();
  80
  81         idle_loop_epilog(in_purr);
  82
  83         return index;
  84 }
  85
  86 static void check_and_cede_processor(void)
  87 {
  88         /*
  89          * Ensure our interrupt state is properly tracked,
  90          * also checks if no interrupt has occurred while we
  91          * were soft-disabled
  92          */
  93         if (prep_irq_for_idle()) {
  94                 cede_processor();
  95 #ifdef CONFIG_TRACE_IRQFLAGS
  96                 /* Ensure that H_CEDE returns with IRQs on */
  97                 if (WARN_ON(!(mfmsr() & MSR_EE)))
  98                         __hard_irq_enable();
  99 #endif
 100         }
 101 }
 102
 103 static int dedicated_cede_loop(struct cpuidle_device *dev,
 104                                 struct cpuidle_driver *drv,
 105                                 int index)
 106 {
 107         unsigned long in_purr;
 108
 109         idle_loop_prolog(&in_purr);
 110         get_lppaca()->donate_dedicated_cpu = 1;
 111
 112         HMT_medium();
 113         check_and_cede_processor();
 114
 115         get_lppaca()->donate_dedicated_cpu = 0;
 116
 117         idle_loop_epilog(in_purr);
 118
 119         return index;
 120 }
 121
 122 static int shared_cede_loop(struct cpuidle_device *dev,
 123                         struct cpuidle_driver *drv,
 124                         int index)
 125 {
 126         unsigned long in_purr;
 127
 128         idle_loop_prolog(&in_purr);
 129
 130         /*
 131          * Yield the processor to the hypervisor.  We return if
 132          * an external interrupt occurs (which are driven prior
 133          * to returning here) or if a prod occurs from another
 134          * processor. When returning here, external interrupts
 135          * are enabled.
 136          */
 137         check_and_cede_processor();
 138
 139         idle_loop_epilog(in_purr);
 140
 141         return index;
 142 }
 143
 144 /*
 145  * States for dedicated partition case.
 146  */
 147 static struct cpuidle_state dedicated_states[] = {
 148         { /* Snooze */
 149                 .name = "snooze",
 150                 .desc = "snooze",
 151                 .exit_latency = 0,
 152                 .target_residency = 0,
 153                 .enter = &snooze_loop },
 154         { /* CEDE */
 155                 .name = "CEDE",
 156                 .desc = "CEDE",
 157                 .exit_latency = 10,
 158                 .target_residency = 100,
 159                 .enter = &dedicated_cede_loop },
 160 };
 161
 162 /*
 163  * States for shared partition case.
 164  */
 165 static struct cpuidle_state shared_states[] = {
 166         { /* Shared Cede */
 167                 .name = "Shared Cede",
 168                 .desc = "Shared Cede",
 169                 .exit_latency = 0,
 170                 .target_residency = 0,
 171                 .enter = &shared_cede_loop },
 172 };
 173
 174 static int pseries_cpuidle_add_cpu_notifier(struct notifier_block *n,
 175                         unsigned long action, void *hcpu)
 176 {
 177         int hotcpu = (unsigned long)hcpu;
 178         struct cpuidle_device *dev =
 179                                 per_cpu(cpuidle_devices, hotcpu);
 180
 181         if (dev && cpuidle_get_driver()) {
 182                 switch (action) {
 183                 case CPU_ONLINE:
 184                 case CPU_ONLINE_FROZEN:
 185                         cpuidle_pause_and_lock();
 186                         cpuidle_enable_device(dev);
 187                         cpuidle_resume_and_unlock();
 188                         break;
 189
 190                 case CPU_DEAD:
 191                 case CPU_DEAD_FROZEN:
 192                         cpuidle_pause_and_lock();
 193                         cpuidle_disable_device(dev);
 194                         cpuidle_resume_and_unlock();
 195                         break;
 196
 197                 default:
 198                         return NOTIFY_DONE;
 199                 }
 200         }
 201         return NOTIFY_OK;
 202 }
 203
 204 static struct notifier_block setup_hotplug_notifier = {
 205         .notifier_call = pseries_cpuidle_add_cpu_notifier,
 206 };
 207
 208 /*
 209  * pseries_cpuidle_driver_init()
 210  */
 211 static int pseries_cpuidle_driver_init(void)
 212 {
 213         int idle_state;
 214         struct cpuidle_driver *drv = &pseries_idle_driver;
 215
 216         drv->state_count = 0;
 217
 218         for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
 219                 /* Is the state not enabled? */
 220                 if (cpuidle_state_table[idle_state].enter == NULL)
 221                         continue;
 222
 223                 drv->states[drv->state_count] = /* structure copy */
 224                         cpuidle_state_table[idle_state];
 225
 226                 drv->state_count += 1;
 227         }
 228
 229         return 0;
 230 }
 231
 232 /*
 233  * pseries_idle_probe()
 234  * Choose state table for shared versus dedicated partition
 235  */
 236 static int pseries_idle_probe(void)
 237 {
 238
 239         if (cpuidle_disable != IDLE_NO_OVERRIDE)
 240                 return -ENODEV;
 241
 242         if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
 243                 if (lppaca_shared_proc(get_lppaca())) {
 244                         cpuidle_state_table = shared_states;
 245                         max_idle_state = ARRAY_SIZE(shared_states);
 246                 } else {
 247                         cpuidle_state_table = dedicated_states;
 248                         max_idle_state = ARRAY_SIZE(dedicated_states);
 249                 }
 250         } else
 251                 return -ENODEV;
 252
 253         if (max_idle_state > 1) {
 254                 snooze_timeout_en = true;
 255                 snooze_timeout = cpuidle_state_table[1].target_residency *
 256                                  tb_ticks_per_usec;
 257         }
 258         return 0;
 259 }
 260
 261 static int __init pseries_processor_idle_init(void)
 262 {
 263         int retval;
 264
 265         retval = pseries_idle_probe();
 266         if (retval)
 267                 return retval;
 268
 269         pseries_cpuidle_driver_init();
 270         retval = cpuidle_register(&pseries_idle_driver, NULL);
 271         if (retval) {
 272                 printk(KERN_DEBUG "Registration of pseries driver failed.\n");
 273                 return retval;
 274         }
 275
 276         register_cpu_notifier(&setup_hotplug_notifier);
 277         printk(KERN_DEBUG "pseries_idle_driver registered\n");
 278         return 0;
 279 }
 280
 281 device_initcall(pseries_processor_idle_init);